Electrical generators are used in a wide variety of applications. Typically, an individual electrical generator operates in a stand-by mode wherein the electrical power provided by a utility is monitored such that if the commercial electrical power from the utility fails, the engine of the electrical generator is automatically started causing the alternator to generate electrical power. When the electrical power generated by the alternator reaches a predetermined voltage and frequency desired by the customer, a transfer switch transfers the load imposed by the customer from the commercial power lines to the electrical generator.
As is conventional, electrical generators utilize a single driving engine coupled to a generator or alternator through a common shaft. Upon actuation of the engine, the crankshaft rotates the common shaft so as to drive the alternator that, in turn, generates electrical power. Typically, prior electrical generators include radiators operatively connected to corresponding engines such that the engine coolant from the engines circulates through the radiators during operation of the engines. A fan, coupled to the crankshaft of the engine, rotates during operation of the electrical generator and draws air across the plurality of radiator tubes of the radiator so as to effectuate the heat exchange between the engine coolant flowing through the plurality of radiator tubes of the radiator and the air within the enclosure. In such a manner, it is intended that the air passing over the radiator tubes of the radiator having a cooling effect thereon so as to maintain the temperature of the engine coolant, and hence the temperature of the engine, below a safe operating limit.
As is known, engine-driven, electrical generators are often exercised to insure proper operation when their use is required. In order to exercise the engine-driven, electrical generator, the engine is either automatically or manually started and run for a predetermined time period at its full operating speed. It can be appreciated that any operation of the engine-driven, electrical generator can produce unwanted noise. The noise generated by the electrical generator during operation is often a result of the rotation of the fan used to cool the engine coolant flowing through the radiator tubes of the radiator of the electrical generator. Consequently, various attempts have been made to limit the time period and the speed at which the fan rotates during operation of the electrical generator to those situations wherein the engine coolant flowing through the radiator must be cooled. By way of example, a sensor may be provided to monitor the temperature of the engine coolant. The fan is operatively connected to the crankshaft of the engine only when the temperature of the engine coolant exceeds a predetermined threshold.
While these prior methods of minimizing the time period for rotating a fan of an engine-driven, electrical generator have been somewhat successful, each of these methods has significant limitations. By way of example, the use of a sensor and the associated electronics for selectively connecting the fan to the crankshaft of the engine can be cost prohibitive. Alternatively, by drawing air inward through the radiator as provided in various automotive applications, it has been found that the thermally responsive clutch interconnects the fan to the crankshaft at the engine for a longer period of time than is necessary to cool the engine coolant flowing through the radiator to a safe operating level. Hence, it can be appreciated that these prior art fan systems will generate more noise than necessary and/or desired by an end user.
Therefore, it is a primary object and feature of the present invention to provide a method for exercising a stand-by electrical generator that insures proper operation of the engine and the electrical generator driven therewith.
It is a further object and feature of the present invention to provide a method for exercising a stand-by electrical generator that generates less noise than prior methods.
It is a still further object and feature of the present invention to provide a method for exercising a stand-by electrical generator that is simple and that is less expensive than prior methods.
In accordance with the present invention, a method is provided for exercising an engine-driven, electrical generator. The generator generates a predetermined output voltage at a predetermined frequency with the engine running a predetermined operating speed. The method includes the steps of selecting a generator exercise mode for the generator and starting the engine. The engine is then run at a predetermined exercise speed that is less than the predetermined operating speed.
In addition, in the exercise mode, the generator generates an exercise voltage that is less than the predetermined output voltage of the generator with the generator in the generator exercise mode. It is contemplated for the exercise speed of the engine to be in the range of 40% to 70% of the predetermined operating speed of the engine. By way of example, when the predetermined operating speed is approximately 3600 revolutions per minute, the predetermined exercise speed is approximately 1800 revolutions per minute. When the predetermined operating speed is approximately 1600 revolutions per minute, the predetermined exercise speed is approximately 1200 revolutions per minute. When the predetermined operating speed is approximately 3000 revolutions per minute, the predetermined exercise speed is approximately 1500 revolutions per minute.
It is contemplated to provide a fuel mixture to the engine when the engine is running at the predetermined operating speed and reducing the fuel mixture provided to the engine with the generator in the generator exercise mode. Further, the output voltage of the generator is changed when the generator is in the generator exercise mode. A transfer switch may also be provided. The transfer switch has a first input connectable to a utility source, a second input operatively connected to the generator, and an output connectable to a load. The transfer switch is selectively movable between a first position connecting the utility source to the load and a second position connecting the generator to the load.
In accordance with a further aspect of the present invention, a method is provided for exercising an engine-driven, electrical generator. The generator generates a predetermined output voltage at a predetermined frequency with the engine running a predetermined operating speed. The method includes the steps of selecting a generator exercise mode for the generator and running the engine at a predetermined exercise speed. The predetermined exercise speed is in the range of 40% to 70% of the predetermined operating speed of the engine. By way of example, when the predetermined operating speed is approximately 3600 revolutions per minute, the predetermined exercise speed is approximately 1800 revolutions per minute. When the predetermined operating speed is approximately 1600 revolutions per minute, the predetermined exercise speed is approximately 1200 revolutions per minute. When the predetermined operating speed is approximately 3000 revolutions per minute, the predetermined exercise speed is approximately 1500 revolutions per minute.
It is contemplated to provide a fuel mixture to the engine when the engine is running at the predetermined operating speed and reducing the fuel mixture provided to the engine with the generator in the generator in the generator exercise mode. Further, the output voltage of the generator is changed when the generator in the generator exercise mode. A transfer switch may also be provided. The transfer switch has a first input connectable to a utility source, a second input operatively connected to the generator, and an output connectable to a load. The transfer switch is selectively movable between a first position connecting the utility source to the load and a second position connecting the generator to the load.
In accordance with a still further aspect of the present invention, a method is provided for exercising an engine-driven, electrical generator. The generator has a first operation mode wherein the generator generates a predetermined output voltage at a predetermined frequency with the engine running a predetermined operating speed and a second exercise mode. In the exercise mode, the engine runs at a predetermined exercise speed in the range of 40% to 70% of the predetermined operating speed of the engine. In addition, in the exercise mode, the generator generates an exercise voltage that less than the predetermined output voltage.
By way of example, when the predetermined operating speed is approximately 3600 revolutions per minute, the predetermined exercise speed is approximately 1800 revolutions per minute. When the predetermined operating speed is approximately 1600 revolutions per minute, the predetermined exercise speed is approximately 1200 revolutions per minute. When the predetermined operating speed is approximately 3000 revolutions per minute, the predetermined exercise speed is approximately 1500 revolutions per minute.